The general goals of this project are to understand the biology of the circulating hormone binding proteins and to delineate the role that they play in human disease. In the current period, we have developed a new method for preparation of radioligands for use in determination of free steroid hormone levels in human plasma. The importance of this methodological advance lies in the fact that the free fraction of plasma hormone closely reflects the portion of hormone that is available to the tissues, which is a key clinical diagnostic measure. In addition, we have made progress in expanding the clinical applications of binding proteins for steroid hormones. We found plasma sex hormone-binding globulin measurements useful in demonstrating thyroid hormone responsivity in familial dysalbuminemic hyperthyroxinemia. Novel evidence of the role of glucocorticoids in regulating both sex hormone-binding globulin and corticosteroid-binding globulin levels in plasma was uncovered in patients with Cushing's syndrome using a glucocorticoid antagonist. Our future research effort will be directed toward developing techniques for assessing intracellular hormone levels using blood specimens obtained in the clinic and correlating this measure with parameters of hormone transport or action in various clinical conditions, especially pregnancy.